Wednesday, August 26, 2009

Drivers Don't See Speeding As A Safety Issue

A study conducted by Purdue University has found that most drivers feel it is safe to exceed the posted speed limit by 5, 10, or 20 mph. That is probably no surprise to anyone who regularly drives on America's roads. In spite of these driver attitudes, the studies continue show that speed kills.

According to an article in "Science Daily", the Purdue survey of drivers found that "21 percent thought it was safe to drive up to 5 mph over the speed limit, 43 percent thought it was safe to drive up to 10 mph over and 36 percent thought it was safe to drive up to 20 mph over the speed limit.According to the researchers, the attitude toward speeding may have something to do with the perception that speed limits are changed for political rather than safety reasons: The repeal of the federal maximum speed limit is most often cited as an example of changing speed limits for political reasons.

The researchers pointed out the need for stricter enforcement of speed limits. They felt that, where speed enforcement is perceived as lax, the statistics show that a driver is 27% more likely to feel that he or she can get away with driving up to 20 mph over the posted speed limit.

Another unrelated study from Australia showed that a driver, whose friends and family approve of his or her speeding, is more likely to drive over the speed limit. When driving, peer pressure apparently works no matter what the age. Where these drivers go wrong is in the assumption that their safety and physical well being aren't affected by increased speeds.

Numerous studies have shown that higher speeds increase the death and injury rates on the highways. When the federal maximum speed limit was reduced to 55 mph in 1974 as a result of the oil crisis, the fatality rate fell by 17 percent within the first year after enactment of the law. In the ten years after the 1995 repeal of the federal maximum speed limit, the figures showed that there were approximately 12,500 more deaths that could be attributed to the increased speeds.

Data from the state of Arizona shows that the state's highway fatality rate fell by 18 percent in the year following installation of speed cameras on major highways. A 2007 National highway and Transportation Safety Administration review of several studies showed that, where speed cameras were used to regulate speed, there were crash reductions of 20 to 25 percent for fixed speed cameras and 21 to 51 percent for mobile speed camera programs.

Several factors come into play when speed is involved. The first is driver distractions. A study published last year by Virginia Tech showed that more than 80 percent of crashes involved some sort of driver distraction within 3 seconds of the crash. The second factor is a driver's reaction time and that ties into the first. If a driver is paying attention to the road ahead, it can take up to 1.5 seconds before the driver perceives an emergency, decides what to do, and then acts on the decision; slamming on the brakes for example. In those 1.5 seconds, a vehicle going 40 mph will cover a distance of more than 88 feet; that is before the car actually begins to slow. At 40 mph, in ideal conditions, it can take almost 170 feet before your car comes to a complete stop. If a driver is distracted, you can add more time and distance to the reaction time and total braking distance.

The third factor is one that few drivers ever take into account; the physics of a car crash. Using a crash force calculator created by the physics department at Georgia State University, figures for the weight of a vehicle along with its speed can be plugged in to show the overall crash forces that the vehicle will experience. For example, a 3,000 pound car traveling at 30 mph will experience a crash force of 45.16 tons. Going from 30 to 40 mph is only a 33 percent increase in speed but it represents a 77 percent increase in crash forces.28 tons of crash force.

It would seem to make sense that a 60 mph crash would be twice as bad as a 30 mph crash but the crash forces are much greater than that. A speed of 60 mph over 30 mph represents a 100 percent increase in speed but it will increase the crash forces by 300 percent.

30 mph crash = 45.16 tons of force

60 mph crash = 180.64 tons of force

Higher speeds increase the distance traveled and decrease the time you have to react to an emergency situation. Higher speeds also increase crash forces exponentially.